Conventionally, there is a thin-film forming apparatus that forms, while continuously paying out and taking up a magnetic recording medium by a roller, a thin film on a base body thereof. Such a thin-film forming apparatus generates plasma by a reaction gas between a can and a first anode arranged to be opposed to the can while bringing the magnetic recording medium into close contact with the rotating can to cause the magnetic recording medium to travel. Accordingly, a protective film is formed on the magnetic recording medium (see, for example, Patent Document 1).
In addition, there is a plasma processing apparatus that performs plasma processing (for example, RIE (Reactive Ion Etching)) while continuously paying out and taking up a plastic film of PET, PI (polyimide), or the like. Such a plasma processing apparatus generates plasma by a process gas between a can and an anode arranged to be opposed to the can while bringing the plastic film into close contact with the rotating can to causing the plastic film to travel. Accordingly, the film is etched and surface modification of the film can be performed.
Incidentally, in such thin-film forming apparatuses or processing apparatuses using plasma, a high-frequency power source is connected to the can and high frequency power is supplied by the high-frequency power source when the can is rotated at a predetermined speed. The rotating can and the stationary high-frequency power source are connected by a rotation introduction unit (not shown) such as a rotary connector using mercury, capacitor coupling constituted of a plurality of opposed flat plates, or a slip ring.
Patent Document 1: Japanese Patent No. 3429369